Light-sensitive material processing basically comprises color developing and desilvering processes; desilvering comprises bleaching and fixing processes or a bleach-fixing process. Rinsing, stabilization and other processes may be added.
In processing solution with bleaching capability used to desilver light-sensitive materials, ferricyanates, bichromates, and other inorganic oxidizing agents have conventionally been widely used to bleach image silver.
However, some critical drawbacks are pointed out in processing solutions with bleaching capability containing these inorganic oxidizing agents. For example, ferricyanates and bichromates are undersirable in preventing environmental pollution in that they may be decomposed by light to produce harmful cyan ions or hexavalent chromium ions, though they are relatively high in image silver bleaching power. Another drawback is that it is difficult to regenerate roy reusing these processing solutions without discarding the waste liquid after processing.
In response to the requirements of less problems of environmental pollution, rapid and simple processing, reuse of waste liquid, and others, processing solutions containing metal complex salts of organic acids, such as aminopolycarboxylic acid, as oxidizing agent have become used. However, such processing solutions are faulty in that the bleaching rate (oxidation rate) of image silver (metallic silver) formed in the developing process is low due to weak oxidation power. For example, iron (III) complex salt of ethylenediaminetetraacetic acid, considered relatively strong in bleaching power among metal complex salts of aminopolycarboxylic acid, is now in practical use in bleaching solutions and bleach-fixers, but it is faulty in that bleaching power is insufficient and much time is taken in the bleaching process when used for high-sensitivity silver halide color photographic light-sensitive materials composed mainly of a silver bromide or silver iodobromide emulsion, specifically silver-rich color paper for picture taking and color negative and color reversal films for picture taking which contain silver iodide.
In addition, developing methods using automatic developing machine etc. to continuously process large amounts of light-sensitive materials necessitate a means of keeping the processing solution components in a given range of concentration to avoid reduction of bleacher performance due to changes in component concentrations. To meet this requirement, as well as to increase economy and prevent environmental pollution, some methods were proposed, including the method in which concentrated replenishers are added in small amounts and the method in which overflow solutions are supplemented with regenerating agents and then reused as replenishers.
As regards bleachers, a method is now in practical use in which a ferrous complex salt of organic acid formed in bleaching developed silver, e.g. iron (II) complex salt of ethylenediaminetetraacetic acid, is oxidized by airation to iron (III) complex salt of ethylenediaminetetraacetic acid, i.e. ferric complex salt of organic acid, and a ragenerating agent is added to replenish the deficient components, then the solution is used as a replenisher.
In recent years, however, what is called compact-labos (also called minilabos) have become widely established with the aim of reducing processing time for silver halide color photographic light-sensitive materials and delivery cost; in these labos, there are severe needs of process simplification and reduction of developing machine installation space, so regeneration is unsuitable since it necessitates troublesome procedures and maintenance, as well as additional processing space.
It is therefore preferable to use the replenishing method with small amounts of thick replenishers without regenerating process; however, when the amount of replenisher is extremely small, there occurs an increase in the concentration of color developer components transferred to the bleaching solution, and the solution becomes likely to be affected by evaporative concentration; these increase the accumulation of color developer components. As stated above, when the color developer component concentration in the bleaching solution increases, there occurs an increase in the ratio of contaminant reducing components, such as color developing agent and sulfites, bleaching reaction is inhibited, and what is called desilvering failure becomes likely to occur. To overcome these drawbacks, it was proposed to use ferric complex salts of aminopolycarboxylic acid disclosed in Research Disclosure No. 24023 and Japanese Patent Publication Open to Public Inspection No. 62-222252/1987 and their mixtures. However, even this method proved to have various drawbacks. For example, ferric propylenediaminetetraacetic acid complex salts are described in the above-given literatures or in the patent publications laid open to public inspection. Such complex salts will produce the so-called sulfurization phenomenon which will decompose thiosulfate that is to serve as a fixing agent, when the complex salts adhered to a light-sensitive material are brought together into a successive fixing or bleach-fixing solution during they are processed, though such complex salts have a strong oxidizing capability. In particular, the above-mentioned disadvantage will be more emphasized when reducing a replenishing amount of a fixing or bleach-fixing solution.
In recent years, `mini-labs` tend to use the so-called waterless treatment, namely, a stabilizing treatment, in which any washing treatment is not carried out, but specific chemicals are used with a great reduction of washing water. In this treatment, unexposed areas tend to be seriously stained while allowing to stand. This tendency is getting more emphasized recently in rapid processing.